- ammonium19
- archegonium23
- ascogonium20
- carpogonium24
- conium14
- decamethonium27
- diazonium24
- euphonium20
- gonium13
- harmonium19
- hexamethonium32
- hormogonium23
- hydronium19
- ionium11
- meconium19
- muonium16
- onium10
- oogonium15
- pandemonium24
- pelargonium22
- peponium19
- phosphonium26
- plutonium19
- polemonium22
- polonium17
- positronium19
- spermagonium25
- spermatogonium27
- sporogonium21
- stramonium18
- sulfonium19
- syconium18
- zirconium26